71 lines
1.8 KiB
Go
71 lines
1.8 KiB
Go
package ratelimit
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import "time"
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// Window is a time windows for counting events within a span of time. The
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// windows slides forward in time so that it spans from the most recent event
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// to size time in the past.
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type Window struct {
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q *queue
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size int64
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}
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// NewWindow creates a new Window that limits the number of events to maximum
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// count of events within a duration of time. The capacity sets the maximum
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// number of events, and size sets the span of time over which the events are
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// counted.
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func NewWindow(capacity int, size time.Duration) *Window {
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return &Window{
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q: &queue{
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buf: make([]int64, capacity),
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},
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size: int64(size),
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}
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}
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// Add attempts to append a new timestamp into the current window. Previously
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// added values that are not within `size` difference from the value being
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// added are first removed. Add fails if adding the value would cause the
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// window to exceed capacity.
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func (w *Window) Add() error {
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now := time.Now().UnixNano()
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if w.Len() != 0 {
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w.q.truncate(now - w.size)
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}
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return w.q.push(now)
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}
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// Cap returns the maximum number of items the window can hold.
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func (w *Window) Cap() int {
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return w.q.cap()
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}
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// Len returns the number of elements currently in the window.
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func (w *Window) Len() int {
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return w.q.len()
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}
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// Span returns the distance from the first to the last item in the window.
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func (w *Window) Span() time.Duration {
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if w.q.len() < 2 {
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return 0
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}
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return time.Duration(w.q.back() - w.q.front())
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}
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// Oldest returns the oldest timestamp in the window.
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func (w *Window) Oldest() time.Time {
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if w.q.len() == 0 {
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return time.Time{}
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}
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return time.Unix(0, w.q.front())
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}
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// Newest returns the newest timestamp in the window.
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func (w *Window) Newest() time.Time {
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if w.q.len() == 0 {
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return time.Time{}
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}
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return time.Unix(0, w.q.back())
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}
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